DNA info
for the Merle Pattern is Mm or MN according to the lab
you use.

The merle gene dilutes random sections of hair to a
lighter color which leaves patches of the original
color. So if you start with a black dog and add the
Merle Gene, you still have a black dog, a black dog with
Merle markings. Unlike the piebald pattern, the patches
may look jagged on the outer edges. Merle affects only Eumelanin, and does not affect Phaeomelanin (red) which
will appear normal. So black, liver, blue or lilac in
the coat, eyes, or nose will be merled.

Black Merle dogs are often called Blue Merle because of
the blue/grey color between the patches in their coat.
This is a widely used term but is not correct.
Technically they should be called black merle. Their
nose pigment is black and their eyes are brown or blue.
If they didn't have the merle gene, they would be solid
black. Blue Merle is misleading because it indicates
that these dogs have blue pigment (dd) when in fact they
have black. It is the PATCHES on the dog that visually
defines the dogs color & what it should appropriately be
called.

In the hierarchy of genes, the Merle Gene overrides the
Dominant Black(SEAL) gene.